As the technological development and demand for mobile apparatuses have increased, the demand for secondary batteries also sharply increases, and among such secondary batteries, lithium secondary batteries which have high energy densities, high operation voltages, and excellent characteristics of preservation and service life are widely being used as energy sources for various electronic apparatuses as well as various mobile apparatuses.
Secondary batteries are roughly classified into cylindrical batteries, rectangular batteries, and pouch-type batteries according to structural features of exterior and interior. Among these, the rectangular batteries and the pouch-type batteries which can be stacked with a high degree of integration and have small widths relative to the lengths thereof particularly have drawn attention.
A secondary battery has an electrode assembly configured from a positive electrode plate, a separator, and a negative electrode plate, and is used such that an external connecting terminal is connected to the electrode assembly. At this point, the external connecting terminal may be connected in a single direction or in dual directions, and each external connecting terminal has one positive electrode terminal and one negative electrode terminal. In addition, when the secondary battery is lengthened in the longitudinal direction, there has been a limitation in that the internal resistance of a battery cell increases due to the resistance of foils constituting the positive electrode pate and the negative electrode plate, and thus, the output of the battery cell is decreased.